Quiet clockwork escapement



Feb. 4, 1969 c. D. VERDE I 3,425,212

QUIET CLOCKWORK ESCAPEMENT Filed May 12, 1967 Sheet I of 2 Feb. 4, 1969 c. D. VERDE 3,425,212

QUIET CLOCKWORK ESCAPEMENT Filed May 12, "1967 Sheet 2 of 2 z/mwme. M Q fizr/zjfl K rk United States Patent Office 3,425,212 Patented Feb. 4, 1969 7 Claims ABSTRACT OF THE DISCLOSURE A clockwork escapement assembly suitable for onepiece molding of the major parts in which resilience is embodied at the points of impact, both at the pallet and the impulse pins, with the direction and extent of the resilience being controlled to minimize the loss of torque to the balance wheel.

Description the invention This invention relates generally to clockwork escapement assemblies and more particularly concerns an escapement in which the major assemblies can be integrally molded and formed with built-in resilience to cushion the impacts that generate tick-tock noise.

It has been recognized that less tick-tock noise will be generated by an escapement if the impacts resulting from driving the balance wheel and intermittently locking the escape Wheel are cushioned by providing resilience in the inter-engaging parts. Such impacts occur when an escape wheel tooth locks against a pallet pin, and when the pallet lever fork impulses the balance wheel. Resilience in the force transmitting parts tends to extend the instant of impact so that there is a less sharp or intense collision. Also, the resilience tends to dissipate a portion of the impact energy as internal friction. As a result, less energy is transmitted from the points of impact to the frame plates, case or other large-surface portion of the clock or timer which serves as the sound radiator that generates" the air-borne tick noise which can be heard.

While resilience will quiet an escapement, it also tends to reduce the amount of energy being transmitted through to the time-rate controlling balance wheel and, as a result, an undesirable drop in balance wheel motion can occur. The amount of distortion permitted by resilience in the escapement must also be controlled since escapements are often called upon to regulate great variations in torque as occur, for example, when a long-running mainspring goes from fully wound to almost run-down.

It is the aim of this invention to provide controlled and directed resilience in an escapement to obtain tick-tock quieting without appreciably affecting force transmission to the balance Wheel. A collateral object is to provide an escapement of the above kind which can function effectively under varying torque loadings.

Another object is to provide an escapement of the type characterized above which can be economically manufactured in that major assemblies are adapted to be molded in one piece of inexpensive plastic material.

Other objects and advantages of the invention will be apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIGURE 1 is a plan view of a clockwork escapement embodying the invention;

FIG. 2 is a fragmentary portion of the FIG. 1 elevation showing the parts in a different operating position; and

FIG. 3 is a side elevation of the escapement shown in FIG. 1.

While the invention will be described in connection with a preferred embodiment, it will be understood that various modes of carrying out the invention will be readily apparent to those skilled in the art without departing from the spirit of the invention.

Turning now to the drawings, there is shown an escapement assembly 10 embodying the invention and including an escape wheel 11, a pallet pin lever 12 and a balance wheel 13. The escape wheel 11 is mounted on a rotatable shaft portion 15 and has a plurality of teeth 16 each with an inclined impulse face 17 and a substantially radial locking face 18. The pallet lever 12 is on an oscillating shaft portion 21 and at one end carries a pair of pallet pins 22 and 23 which cooperate with the escape wheel teeth 16, and at the opposite end is formed with a fork portion 24. The balance Wheel 13 includes a hub portion 26 which is secured to a shaft 27 and the balance wheel carries an impulse pin 28 which cooperates with the lever fork portion 24. A hairspring 29 having its outer end anchored is locked at its inner end in a slotted collar 30 formed on the hub portion 26.

As will be apparent to those familiar with this art, when the balance wheel 13 swings counterclockwise from the position illustrated under the force of the hairspring 29, the impulse pin 28 enters the lever fork portion 24 and swings the lever 12 clockwise so as to lift the pallet pin 23 from the locking face 18 of the adjacent tooth 16 while, at the same time, shifting the pallet pin 22 toward the path of the next escape wheel tooth. The escape wheel 11 is thus released and mainspring power drives the escape wheel clockwise. The escape wheel moves clockwise as soon as the pin 23 clears the locking face of the adjacent tooth, and hence the impulse face 17 of that tooth strikes the pin 23 (the position shown in FIG. 2) to impart a clockwise torque on the pallet pin lever 12. This energy is transmitted from the fork portion 24 0f the lever 12 in the form of a sharp blow delivered to the impulse pin 28 that tends to drive the balance wheel 13 counterclockwise. The driving energy imparted to the balance wheel is gradually absorbed by the hairspring 29 as the balance wheel makes its full, counterclockwise swing, and the tensioned hairspring then drives the balance wheel clockwise.

In the meantime, as soon as the pin 23 clears the adjacent tooth impulse face 18, the escape wheel 11 is completely freed and the full power of the mainspring drives the wheel clockwise until the pin 22 is struck by the locking face 18 of the next tooth. The escapement remains locked until the balance wheel 13 returns in its clockwise swing and the impulse pin 28 swings the lever 12 counterclockwise. This unlocks the escape wheel 11, impulses the balance wheel clockwise, and returns the parts to their FIG. 1 positions.

As can be seen in FIG. 1 and as will be appreciated by those skilled in this art, the locking faces 18 of the escape wheel teeth 16 are somewhat undercut rather than being truly radial. Thus, the lever 12 is banked by engagement of a pallet pin with the cylindrical root portion of the escape wheel 11 and is held locked by the undercut locking face 18 of the adjacent tooth that is pressed againstthe pin under mainspring force. For shock protection, a safety roller 33 is mounted on the balance wheel shaft 27 in position to cooperate with a guard finger 34 at the forked end of the lever 12. The roller 33 has a peripheral slot 35 alined with the impulse pin 28, and the finger 34 is alined with the fork portion 24. When the pin 28 enters the fork portion 24, the finger 34 also freely enters the slot 35. Thus, if a jar dislodges a pallet pin from a locking-face 18 while the pin 28 is free of the fork portion 24, the guard finger 34 will engage the periphery of the safety roller 33 and prevent overbanking.

In carrying out the invention, the major units of the escapement are molded of resilient plastic material, preferably-as integral parts. The escape wheel 11 and its shaft portion 15 are formed integrally, and an enlarged portion of the shaft 15 is shaped to define a pinion gear 40 which couples the escape wheel 11 to the timing train and the mainspring force. The lever 12, pallet pins 22 and 23, fork portion 24 and guard finger 34 are all preferably molded integrally. The balance wheel 13, impulse pin 28 and hairspring collar 30 are formed integrally of resilient plastic, and, in the illustrated construction, the shaft 27 on which the balance wheel assembly is mounted, is formed of steel which constitutes a better bearing material and hence facilitates accurately-timed oscillations of the balance wheel.

In accordance with the invention, the pallet pins 22, 23 and the impulse pin 28 are supported through narrowedor necked-down pin support portions which give resilience to quiet the escapement, but the resilience is directed and limited so as not to adversely affect the timekeeping functions of the escapement. The impulse pin 28 is formed at the end of a pin support portion 41 lying radially, and in the plane of, the balance wheel 13. The portion 41 is faired smoothly into the body of the wheel 13 so as to serve as a spring when the fork portion 24 strikes the impulse pin at right angles to the support portion 41 as the balance wheel is driven to wind up the hairspring 29. The pin end of the support portion 41 is closely sandwiched by a pair of shoulders 42 and 43 on the body of the balance wheel 13 so that flexure of the portion 41 is limited and controlled.

To keep the mass of the balance wheel assembly 13 centered on its shaft 27, a pair of lightening holes 44 are preferably formed on the opposite sides of the shaft from the impulse pin 28. The material removed to form the holes 44 about equals that portion of the material emoved to define the impulse pin support portion 41.

The pallet pins 22, 23 are supported on narrowedor necked-down, resilient pin support portions 46 disposed along lines generally parallel to the locking face and generally perpendicular to the impulse face of the escape wheel tooth then acting on the pins. In this way, the portions 46 act as springs giving maximum resilience to the pins 22, 23 when they are struck by the locking faces 18 of the adjacent teeth 16 (see pin 23 in FIG. 1), whereas the portions 41 afford little resilience to the pins 22, 23 when the pins are struck by the impulse faces 17 of the adjacent teeth (see FIG. 2). As a result of this arrangement, the locking collision between the locking faces 18 of the teeth 16 and the pallet pins 22, 23, which does no useful work and which is the greatest cause of tick-took noise, is cushioned by the resilience of the pallet pin support portions 46. However, the force imparted by the impulse faces 18 of the escape wheel teeth on the pallet pins to drive the balance wheel 13 is not dissipated by the appreciable fiexure of the pin support portions 46. Thus, the resilience which helps achieve quieting of the escapement does not also tend to reduce balance wheel motion.

Since the locking faces of escape wheel teeth are somewhat undercut rather than being truly radial, an escape wheel must normally back up slightly to permit the pallet pins to unlock the esc'ape;rne :nts In the present case, because of the resilience of the pin support portions 46, unlocking can be accommodated by fiexure of the pin support portions, and thus reverse movement of the escape wheel and the gear train against the force of the mainspring is avoided. It has been found that by avoiding this reverse, unlocking movement of the escape wheel, a smooth, more regular flow of power is obtained which results in better timekeeping accuracy.

In forming the pallet pin lever 12, the pin support portions 46 and the pallet pins 22, 23, pairs of shoulders 48 are disposed to closely embrace the bases of the pallet pins. In this way, the amount of pin flexure is closely controlled and thus the escapement is able to handle varying torque loadings as might be obtained through the unwinding cycle of a mainspring.

It can thus be seen that an escapement has been provided in which there is controlled and directed resilience to obtain tick-tock quieting without appreciably affecting force transmission through the balance Wheel. Moreover, the positioning of the shoulders adjacent to the resilience producing supports for the pallet pins and the impulse pin enable the escapement to function effectively under varying torque loadings.

While the resilience of the portions 41 and 46 lessens the factor which creates noise, it is also true that the configuration of the parts acts in other ways to reduce the sound which is eventually heard. First, it can be seen that impact energy, in order to reach the shaft portions and the sound radiating frame plates, must follow curved paths through the necked-down portions 41, 46 so that the energy is more readily dissipated in internal friction. Second, instead of there being one sharp impact, a multiple impact results from first the pins 23, 28 being struck and then the adjacent shoulders 42, 43, 46 being engaged. The resulting multiple vibrations coming from different points at slightly different instants creates a sort of energy wave impedance that tends to decay the total amount of energy before it reaches the larger, sound radiating portions of the movement in which the escapement is used.

It can also be appreciated that an escapement of this kind can be very economically formed in that the major assemblies can be injection molded in one piece of inexpensive plastic material.

I claim as my invention:

1. An escapement for minimizing the generation of tick-took noise comprising, in combination, a journalled escape wheel having teeth with substantially radial locking faces and inclined impulse faces, a pallet lever journalled adjacent said escape wheel and having a pair of pallet pins extending at right angles to, and alternatively in the path of, said escape wheel teeth, said pins being connected to said lever by narrowed, resilient pin support portions, and said portions being disposed along a line generally parallel to the locking face and generally perpendicular to the impulse face of the escape wheel tooth then acting on the pins of the respective pin support portions.

2. The combination of claim 1 in which said pin support portions lie in the plane of said lever and the lever is formed with shoulders on either side of said portions so as to limit the flexure thereof.

3. The combination of claim 1 in which said lever, said pins and said pin support portions are formed integrally of resilient material.

4. The combination of claim 1 in which said lever has a forked end, and the combination including a balanced wheel journalled adjacent the forked end of the lever, an impulse pin on said balance wheel extending through said forked end of the lever, said impulse pin being connected to said balance wheel by a resilient pin support portion lying radially, and in the plane of, said balance wheel.

5. The combination of claim 4 in which said balance wheel, said impulse pin and said impulse pin support portion are formed integrally of resilient material.

6. In an escapement assembly including an escapement wheel, pallet pin lever with pallet pins and balance wheel with impulse pin, the improvement comprising, said lever and pallet pins being formed integrally of resilient material, said balance wheel and impulse pin being formed integrally of resilient material, and said pins being repectively mounted through narrowed portions of said material constituting resilient mountings for said pins.

7. The improvement of claim 6 in which said portions are disposed between opposed shoulders formed on the lever and the wheel, respectively, to limit fiexure of the portions and resulting movement of the pins.

References Cited UNITED STATES PATENTS 3/1942 McCullough 58-117 10/1946 Rhodes 58117 9/1955 Linard 58-121 6/ 1964 Dinerstein et al 58-116 FOREIGN PATENTS 1/ 1934 France. 9/ 1955 France.

OTHER REFERENCES German printed application, 1,233,783.

RICHARD B. WILKINSON, Primary Examiner.

S. A. WAL, Assistant Examiner.

U.S. Cl. X.R. 

